email them again, or call them, there should be a way to draw their attention, they will take it seriously

Is the 5GHz led still lit up? If not, push WPS button on the extender and your router, or login the extender to configure it again. If the 5GHz extended network disappears, check your router. Make...

Do you choose the correct time zone? The time won't change?

Tplink smart plug does not support that feature. You can check power usage of HS110 on the app though

They said it's a display issue, actually it's on 11ac. They provided a link of a driver that address this problem. I didn't install it. http://support.tp-link.com/f/8813732dcd/?dl=1

What's the hardware version of your extender? Are you not able to choose your time zone? Select the correct time zone, then the current time will change.